Abstract

Farmers, agents and shops were interviewed to elucidate the postharvest handling practices of raw milk on the informal milk market in Kiambu County, Kenya. Interviews were also conducted to ascertain the knowledge and precautions taken by the farmers to prevent the presence of antibiotic residues in the milk. Raw milk was sampled and analysed to assess the microbial quality and to determine if physical or chemical adulteration, in terms of added water, antibiotic residues and hydrogen peroxide, were present.

The farmers knew little about their antibiotic use and many farmers could not remember the last time they used antibiotics, mainly because it was a long time ago but also due to a minimal or lack of interest in how the veterinarian treated the cow. Two of the farmers stated that they used hot water to ensure their personal hygiene while handling milk. The seven remaining farmers declared they did not take any measures to ensure their personal hygiene. All small-scale agents used plastic jerry cans to hold their milk, while all large-scale agents used aluminium cans. Microbial results did not differ significantly between small- and large-scale agents (p > 0.05) despite their diverse equipment. Farmers had a significantly longer experience than all other milk handlers along the value chain (p < 0.001). When it comes to milk handling education, 2 of 9 (22%) farmers had received visits from dairy societies for educational purposes while 12 of 17 (71%) agents declared they regularly attend seminars for educational purposes, or had participated in a course to get a certificate in milk handling. Of the shops, 4 of 11 (36%) employees stated they had attended at least one seminar held by the Kenya Dairy Board. Farmers, agents and shops held their milk an average of 5.4, 6.8 and 16 hours, respectively. Cold water immersion was used by 6 of 9 (66%) farmers as a form of preservation. Among the agents only one (6%) practiced partial cold storage whereas the rest stored at ambient temperature. Between the several types of shops, the preservation options were mixed and 7 of 11 (64%) practiced full or partial cold storage. Quality control was present along the whole value chain, although around 55% of the farmers did not implement any type of quality check of their milk. All agents and shops regularly monitored their milk.

The microbial counts in farmers’ milk (Staphylococcus aureus, coliforms and total plate count (TPC)) were significantly lower than in milk from the agents (p < 0.001), implying that farmers’ milk was of better microbiological quality. Statistical analysis of TPC and coliform counts showed significant differences (p < 0.001 and p < 0.05, respectively) between farmers and shops’ milk, implying that farmers’ milk was of better quality with regard to microbial counts. The lower counts in farmers’ milk indicated that there was deterioration along the supply chain due to the proliferation of the microorganisms initially present in the milk or/and due to cross contamination. No significant difference in milk quality between other steps in the value chain could be detected.

According to the East African Raw cow milk standard 3 of 18 (17%) samples from the farmers’ milk and 59% and 64% of agents and shops’ milk samples, respectively, exceeded the threshold limit of 5.0x104 cfu/mL with regard to coliform counts. Furthermore, 1 of 18 (5%) of farmers and 59% and 45% of agents and shops’ milk samples, respectively, exceeded the threshold limit of 2.0x106 cfu/mL with regard to TPC.

Adulteration was detected in terms of specific gravity in 30% of all the samples along the value chain according to the East Africa Raw cow milk standard. Chemical adulteration was detected in one sample from a large-scale agent, in the form of hydrogen peroxide. Confirmed detection of antibiotic residues could not be found in any sample.Handling practices clearly indicated that the value chain from farmer to agent is in need of accessing appropriate technology and equipment for safe milk handling. However, virtually all consumers boil purchased raw milk before consumption. Risks of infection from bacterial health hazards are therefore considered to be low. Poverty seems to be the main contributor to the lack of resources. Appropriate innovations, which are cost-effective and affordable to all market players involved, will be necessary to ensure proper milk handling.

Main title:

Quality analysis of raw milk along the value chain of the informal milk market in Kiambu County, Kenya